Partially processed or fully processed food products are derived from various raw foodstuffs and customers, including domestic consumers and restaurants, welcome the provision of such processed food in a form which can be quickly readied for presentation to the ultimate consumer, often with a brief heating or food processing step. For example, outlets wishing to serve french-fries can have the convenience of purchasing bulk packs of frozen vegetable which can be brought to a predictable and attractive form by a brief period of cooking either with a deep frying technique or an oven technique.
Thus, there is a major demand in the market of many countries for products such as french-fried potato chips produced by cutting the potatoes into elongate square cross-sectional chips which are deep fried to produce chips to produce an appetising hot product. The product desirably has an attractive coloured exterior with a crunchy shell and a soft mealy interior. Thus, there is a major market for frozen, partially pre-fried potato chips (known as par-fried potatoes), and this approach simplifies storage and inventory control to outlets while assuring uniform quality between batches. Time and delay at an outlet and avoiding what would otherwise be considerable labour costs in processing french-fries from raw potatoes is achieved.
A typical process for producing a 10 mm frozen french-fry is as follows:                (a) Potatoes are firstly washed and then sometimes graded for quality and size for different product runs.        (b) The potatoes are peeled typically by a steam process with steam at high pressure and high temperature of around 200° C. for around 14 seconds.        (c) The potatoes are cut into elongate strips e.g. square cross-section of around 10 mm sides, conveniently in a water knife cutting or similar process.        (d) The potato strips are further processed to remove the defective strips and eyes, and then washed.        (e) Potato strips are blanched in a hot water process with this step reducing excess free sugars from the surface of the strips and to transform enzymes so as to be inactive. Sometimes the blanch is in two stages, namely a high temperature strep of around 83° C. for a few minutes followed a low temperature step typically around 73° C. for often a longer period.        (f) A drying process is effected to reduce the water content of the blanched strips. A weight loss of around 12% typically occurs where the drying process is around 60° C.        (g) Par-frying of the potato chips is effected in hot oil at around 190° C. for a suitable time of around 50 seconds.        (h) Lastly freezing is effected to freeze the potato chips down to a temperature of around −18° C. ready for packing, and for storage and distribution.        
Frozen potato chips produced as described above typically will be suitable to be finish fried at a serving location in suitable oil at about 180° C. for around 3 minutes. It is recognised that such hot chips need to be produced at an outlet in batches, but the holding time post-frying is short and therefore smaller, more frequent batches of chips need to be prepared and in many instances chips are discarded because they have texturally decayed. Such hot chips are liable to become gradually limp when holding due to migration of moisture from the product interior to the surface.
Apart from a long-standing desirability where possible to provide for economic processing and possibly improving consumer appeal and satisfaction for final product, it is has also been long recognised there is significant absorption of cooking oils into starch products such as french-fries which are cooked by frying. Adverse health implications are well understood to exist with foods with relative high fat levels and, at least for french-fries, the well established processes have an inevitable high fat content in the final product.
Despite the characteristics of present food processing, the processing of starch foods such as potatoes into products such as french-fries has essentially remained an industry with little change over an extended period.
Broadly, the present invention is concerned with devising different processes for starch-based foods which offer the potential for distinct and useful changes to methods, apparatus and/or products in the food industry.